X-ray device



Jul 29, 1924.

, W. D. COOLIDGE X-RAY DEVICE Filed June so. 1919 Inventor WilliamDCOOIidQe,

7 MW v:

His Attorney.

Patented July 29, 1924.

UNITED STATES PATENT OFFICE.

W D. OOOLIDGE, O]? SCHENEOTADY, NEW YORK, ASSIGNOB '10 GENERAJHELIO-TRIO COMPANY, A CORPORATION OF NEW YORK.

x-RAY DEVICE.

Application filed June 80, 1919. Serial No. 807,814.

To all whom it may concern.

Be it known that I, WILLIAM D. Coomnon, a citizen of the United States,residin at Schenectady, county of Schenectady, tate of New York, haveinvented certain new and useful Improvements in X-Ray Devices, of whichthe following is a specification.

The present invention comprises an X-ray tube capable of substantiallysilent operation, that-is without the hissin and crackling noises whichacoompanie the operation of X-ray tubes as formerly constructed. I havediscovered that when the thickness of the glass wall of an X-ray tube ismaterially increased that the crackling noises formerly attendant on theoperation of an X-ray tube are substantially eliminated, and that theoperation of the tube accordingly is free from the current fluctuationsaccoman no-is operation.

p l h a beenzustomary to make X-ray tubes about 0.02 inch in thickness,that is, as thin as permissible without collapse of the bulb under theinfluence of the external atmospheric pressure. In accordance with myinvention the walls of the entire tube or at least the part of the tubedirectly surrounding the cathode and the anode head are made of glasshaving a thickness greater than about inch and preferably a thickness ofabout inch. Preferably the tube consists in part of lead glass and isprovided with a thin window consisting of material transparent to X-rayssuch as lime glass.

The accompanying drawing illustrates an X-ray tube embodying myinvention, shown partly in section.

Referring to the drawin the X-ray tube illustrated comprises a big yevacuated envelope 1 comprising a somewhat bulbous electrode chamber 2,and outwardly extending arms 3, 4, into which are sealed the conductorsfor the cathode 5, and the anode 6. The cathode and the anode are ofusual wellknown construction, the cathode comprising an incandescentfilament of tungsten, or other refractory metal (shown by a dotted line)and the anode of a block of copper containing a button of tungsten (alsoshown in dotted outline). The anode stem 7 projects outside the tubeenvelope and external to the tube carries a radiator 8. The structuraldetails are similar to the radiator type of tube shown and described byme on page igltf the General Electric Review, January,

The wall of the electrode chamber 2 which closely surrounds theelectrodes consists of lead glass about 1 inch in thickness, the walltapering in the tube illustrated to a lesser thickness for the cathodeand anode arms. In some cases the thickness of the glass may be uniformthroughout the tube except for a window 9 opposite the face of the anodeconsisting of material permeable to X-rays such, for example, as limeglass. The lime glass window is slightly concave and is sealed to thelead glass bulb on a slightly progecting lip, as indicated in thedrawing and preferably is thinner walled than the electrode bulb so asto reduce the absorption of X-rays thereby. As shown in the drawing, theenvelo e has a substantially tubular shape and so 0 osely surrounds theelectrodes that the electrode chamber 2 constitutes but a slightenlargement. The window 9 although slightly concave to secure mechanicalstrength in general conforms to the general contour of the envelope.This construction rendersthe device especially suitable when compactnessand light weight is desired, and simplifies its manufacture.

In my opinion the quietness and stability of operation of a thick-walledbulb is to be ascribed to the smaller-electrostatic capacity of thethick-walled tube. In an X-ray tube the inside surface of the tube wallbecomes electrostatically charged by the electrons emitted from thecathode and this electrostatic charge is bound by an equal charge ofopposite polarity on the outer conducting surface of the tube. When highfrequency surges are set up for any reason the variation inelectrostatic charge produces the crackling noise observed in theoperation of the ordinary thin-walled X-ray tube. With a thick-walledtube the electrostatic condenser action is very much decreased. It islikely that there is also some leakage of electricity through the glasswhich is responsible in some measure for the crackling noise. It isevident, however, that the benefits of my invention are securedirrespective of what may be the theory of the cause of the cracklingnoise as formerly observed.

It is not essential that an X-ray tube embodying my invention shallconsist in part of lead glass in order to possess the property of silentoperation. I have found thickwallcd tubes consisting entirely oflead-free glass may also be operated noiselcssly. Of course, the heavylead glass possesses the cided advantage of giving better protection tothe operator.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. An X-ray tube adapted for substantially inaudible operationcomprising a cathode adapted' to operate at incandesccnce, an anode andan enclosing evacuated envelope of glass closely surrounding saidelectrodes having a thickness of the order of about one-fourth inch.

2. An X-ray device comprising cooperating electrodes, an enclosingevacuated envelope of substantially tubular shape consisting of leadlass being materially greater than oneeight inch thickness at regionsclosely adj acent said electrodes so as to be capable of silentoperation, and having opposite said anode a thinner window ofsubstantially lead-free glass sealed into said envelope and conformingsubstantially to the general contour of said envelope.

3. An X-ray device comprising cooperating electrodes, an envelopeclosely surrounding said electrodes and having, at the region adjacentsaid electrodes, a wall of suflicient thickness to prevent substantiallythe electric disturbances in the operation of the device which causecrackling noises, and a window consisting of material permeable to X-rays scaled into said envelope in the path of X-rays generated by saiddevice.

4. An X-ray tube comprising cooperating electrodes, and an envelopetherefor having a wall of sufficient thickness to substantially preventthe occurrence of high frequency surges during the operation of saidtube, said envelope being provided adjacent the anode with a windowconsisting of material permeable to X-rays, the portions of saidenvelope adjoining the window being spaced as closely to the electrodesas said window.

5. An X-ray device comprising a filamentary cathode capal'le ofoperating at incande'scencc, an anode of materially greater mass and anenvelope closely surrounding said electrodes consisting of lead glasshaving a thickness approximating about onefourth inch and having athinner window of curved surface and consisting of lime glass sealedtherein, the space within said envelope being evacuated to a. pressureso low that gas ionization is inappreciable during operation.

In Witness whereof, I my hand this 27th day of have hereunto set June,1919.

WILLIAM D. COOLIDGE.

